Giải phương trình: \[\frac{{4x}}{{{x^2} + x + 3}} + \frac{{5x}}{{{x^2} - 5x + 3}} = - \frac{3}{2}\].

\[\frac{{4x}}{{{x^2} + x + 3}} + \frac{{5x}}{{{x^2} - 5x + 3}} = - \frac{3}{2}\]

\[ \Leftrightarrow \frac{{4x\left( {{x^2} - 5x + 3} \right) + 5x\left( {{x^2} + x + 3} \right)}}{{\left( {{x^2} + x + 3} \right)\left( {{x^2} - 5x + 3} \right)}} + \frac{3}{2} = 0\]

\[ \Leftrightarrow \frac{{8x\left( {{x^2} - 5x + 3} \right) + 10x\left( {{x^2} + x + 3} \right) + 3\left( {{x^2} + x + 3} \right)\left( {{x^2} - 5x + 3} \right)}}{{2\left( {{x^2} + x + 3} \right)\left( {{x^2} - 5x + 3} \right)}} = 0\]

\[ \Rightarrow 8x\left( {{x^2} - 5x + 3} \right) + 10x\left( {{x^2} + x + 3} \right) + 3\left( {{x^2} + x + 3} \right)\left( {{x^2} - 5x + 3} \right) = 0\]

\[ \Leftrightarrow 3\left( {{x^2} - 3x + 3} \right)\left( {{x^2} + 5x + 3} \right) = 0\]

\[ \Rightarrow \left[ \begin{array}{l}{x^2} - 3x + 3 = 0\\{x^2} + 5x + 3 = 0\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}VN\\x = \frac{{ - 5}}{2} \pm \frac{{\sqrt {13} }}{2}\;\left( {TM} \right)\end{array} \right.\]

Vậy nghiệm của phương trình là \[x = \frac{{ - 5}}{2} \pm \frac{{\sqrt {13} }}{2}\].